Enhancement of burning rate process of solid propellant compositions using radiation

ABSTRACT

The irradiation and use of a catalytic agent which undergoes rapid and controlled decomposition after said irradiation, said catalytic agent being used in a solid propellant composition, and said irradiation preferably taking place upon ignition of the solid propellant composition.

United States Patent inventor David C. Sayles Huntsville, Ah.

July 20, 1967 July 6, 1971 The United States of America as represented by the Secretary of the Army Appl. N 0. Filed Patented Aseignee ENHANCEMENT OF BURNING RATE PROCESS OF SOLID PROPELLANT COMPOSITIONS USING RADIATION 1 Claim, 1 Drawing Fig.

US. Cl 60/219, 149/.19, 149/20 Int. Cl. C06d 5/06, F23r 1/1 8 Field of Search 149/ 19,

[56] References Cited UNITED STATES PATENTS 3,339,537 8/1968 Picquendar 60/254 3,213,173 10/1965 Cobb 149/19X 3,214,306 10/1965 Colichman 149/19 X 3,322,804 5/1967 Pruett 149/109 X 3,336,751 8/1967 Rifkin etal. 60/218 3,070,470 12/1962 Argabright et a1 149/19 Primary ExaminerBenjamin R. Padgett Attorneys-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and Elihu L. Turetsky ABSTRACT: The irradiation and use of a catalytic agent which undergoes rapid and controlled decomposition after said irradiation, said catalytic agent being used in a solid propellant composition, and said irradiation preferably taking place upon ignition of the solid propellant composition.

NITROGEN STORAGE CONTAINER PATENTEU JUL-6 I97! David C. Suyles,

INVENTOR. H 771-5444 BY My.

Huh/ M gzb WTTORNEYS ENHANCEMENT OF BURNING RATE PROCESS OF SOLID PROPELLANT COMPOSITIONS USING RADIATION BACKGROUND OF THE INVENTION This invention relates to a method of enhancing the burning rate of solid propellant compositions, and particularly to a method for radically increasing the burning rate of solid propellant compositions through the use of catalytic agents.

In the operation of jet motors, it is customary to burn such solid propellant charges in the motor chambers to produce gases under pressure, which escape at high velocity, generally through an exhaust nozzle leading from the chamber, thereby producing a resultant thrust. The combustion of a solid propellant is generally considered to be an exothermic reaction between gases evolved from the thermal decomposition of the oxidizer and the fuel. The intensity of the thrust produced is determined by the rate at which the propellant burns.

As the usefulness of a propellant composition is dependent upon the intensity of thrust created by its combustion and the consistent reproducibility of said thrust, it has long been the objective of those engaged in the art to find a means of increasing the buming rate while at the same time decreasing the effect of propellant temperature upon either or both the burning rate and the equilibrium chamber pressure.

Accordingly, the principal object of this invention is to find a novel means of enhancing the burning rate of solid propellant compositions while minimizing the accompanying disadvantages.

It is a particular object of this invention to increase the burning rate of solid propellant compositions through the use of catalytic agents.

These and other objects and advantages of this invention will become more readily understood and apparent as the same is understood by reference to the following detailed description, when read in conjunction with the accompanying drawing, which forms an integral part thereof.

SUMMARY OF THE INVENTION It has been discovered that the burning rate of solid propellant compositions can be radically increased through the use of catalytic agents which undergo rapid and controlled decomposition when stimulated by radiation.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a schematic representation, greatly exaggerated for emphasis, of the preferred embodiment of this invention, showing the radiation source and an actuation mechanism therefore located in a missile.

DESCRIPTION OF THE PREFERRED EMBODIMENT This invention employs a radiation source to irradiate a catalytic agent (which undergoes rapid and controlled decomposition when stimulated by the radiation source) in order to increase the burning rate of solid propellant compositions.

In the preferred embodiment of this invention, an X-ray and beta-ray radiation source (Promethium-l47) is used. However, the radiation source may be any other radiation source (e.g., Cobalt-60). In other words, any source of alpha-, beta-, or X-ray (gamma) radiation may be employed.

This Promethium X-ray and beta-ray source is the size of a pack of cigarettes and has recently been built under the spon sorship of the Atomic Energy Commission. However, this source is not now commercially available. Therefore, if desired, similar radiation sources may be employed instead.

Referring now to the single FIGURE, a missile containing a solid propellant grain 12 (which includes a catalytic agent of this invention) is shown. Inside grain perforation 14 is a lead container 16 having thermal insulation 18 therearound. For purposesof illustration the structure of the container 16 with the radiation source 24 therein, the container 16 is shown considerably exaggerated in size relative to the propellant grain 12 and missile 10. A tungsten-stainless steel alloy closure cap 20 is attached to rod 22. When radiation source 24 is not in use, a retaining spring 26 holds the closure cap 20 in a closed position so as to prevent the leakage of radioactive particles from the radiation source 24. A safety shear pin 28 is used in addition to the retaining spring 26.

In order to irradiate the catalytic agent (preferably upon ignition of the propellant grain), nitrogen gas from nitrogen storage container 30 is fed through an electric squib-actuated valve 32 into cylinder 34, thus causing the rod 22 and closure cap 20 to move to the position shown, by breaking safety shear pin 28 and compressing retaining spring 26, and thereby irradiating the catalytic agent in the solid propellant grain 12.

As mentioned earlier, the preferred radiation source 24 is a pellet of Promethiuml 47.

The pellet of radioactive Promethium-l47 has a half-life of 2.6 years, and emits beta-excited X-rays.

The catalytic agent is nickel (IV) tetracarbonylacrylonitrile adduct or a radiation-sensitive chemical which can be any of the complexes resulting from the reaction of silver perchlorate with hexane, silver perchlorate with alphapinene, and silver perchlorate with various alkynes.

Generally speaking, any metal salt adduct of an alkene or an alkyne may be employed. However, transition (Group VIII) metals are preferred.

The catalytic or radiation-sensitive chemicals are incorporated into the solid propellant formulation during the process of manufacture.

A typical solid propellant formulation also contains an organic material as the combination binder fuel, and a solid oxidant such as ammonium nitrate. Other inorganic oxidizing salts may be employed. Particularly useful inorganic oxidizing salts include the ammonium, alkali metal, and alkaline earth metal salts of nitric, perchloric and chloric acids and mixtures thereof, such as sodium, potassium, magnesium and ammonium perchlorates, lithium and strontium chlorates, and potassium, sodium, calcium and ammonium nitrates.

The combination binder fuel utilized in the propellant formulations of this invention can be a polymer prepared from a wide variety of materials. Typical examples are carboxyl-terminated polybutadiene and polybutadiene-acrylic acid binders.

The propellant formulations of this invention can contain in addition to the combination binder fuel and catalytic agent a powdered metal such as aluminum and various compounding ingredients commonly employed in making solid propellants, such as plasticizers, oxidation inhibitors, reinforcing agents, wetting agents, modifiers, vulcanizing agents, curing agents, other accelerators and burning rate catalysts, and the like.

Other powdered metals (e.g., boron, magnesium and beryllium) may be used. Alloys can also be used such as the aluminum alloys of boron, magnesium, manganese, copper and the like. Silicon can also be used.

The propellant is ignited by conventional igniter means and it is a definite advantage to start the irradiation of the catalytic agent simultaneously with ignition of the propellant. However, it is also possible to irradiate the catalytic agent before or after ignition of the propellant. The catalytic agent responds during combustion to a relatively low order of radiation and, on undergoing decomposition, will greatly increase the rate of propellant burning.

Although the nature of the reaction, which is undergone during the combustion of the propellant, has not been conclusively proven, it has been hypothesized that the increase in the burning rate of the propellant is a result of the heat liberated by the decomposition of the catalytic agent as well as by its catalytic action.

While this invention has been described with reference to a I preferred embodiment thereof, it will be apparent that various other modifications and variations will occur to those skilled in the art in the light of the above teachings, which modificaadduct, the adduct of silver perchlorate with hexene and the adduct of silver perchlorate with alpha-pinene with a radiation source of alpha-, betaor X-ray radiation mounted adjacent said propellant composition for irradiating said propellant composition to cause decomposition of said metal salt adduct and thereby increase the potential rate of propellant burning. 

1. The method of producing thrust in a solid propellant rocket motor which comprises burning a propellant composition including an organic material as a combination fuel binder, an inorganic oxidant, a metal salt adduct selected from the group consisting of nickel (IV) tetracarbonyl-acrylonitrile adduct, the adduct of silver perchlorate with hexene and the adduct of silver perchlorate with alpha-pinene with a radiation source of alpha-, beta- or X-ray radiation mounted adjacent said propellant composition for irradiating said propellant composition to cause decomposition of said metal salt adduct and thereby increase the potential rate of propellant burning. 